UICollectionView with self-sizing cells resizes cells during insert/remove animation

I ran into this, and it took me a while to figure out that the size it was reverting to was the estimated size.

I think I figured out a workaround:

• Keep one instance of your self-sizing cell class around
• Implement sizeForItemAtIndexPath, and configure that cell instance with data for that index path, then ask it for its preferred size (systemLayoutFittingSize).
• Cache this information in a dictionary for performance.

See example project here.

1. Set estimatedItemSize property to some appropriate size.

2. In your custom UICollectionView class override below method and cache layoutAttributes's size given by super.

   -(UICollectionViewLayoutAttributes*)preferredLayoutAttributesFittingAttributes:(UICollectionViewLayoutAttributes *)layoutAttributes{    UICollectionViewLayoutAttributes * superAttr = [super preferredLayoutAttributesFittingAttributes:layoutAttributes];   //Cache size which is returned by super (superAttr.frame.size) since super calculates the correct size for auto size cells.    return superAttr;}

3.In sizeForItemAtIndexPath return cached size if available else estimated size.

-(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {    //return cached size if available else the estimated size}

To avoid cell resize use InvalidationContext

    let context = UICollectionViewFlowLayoutInvalidationContext()    context.invalidateFlowLayoutAttributes = false    collectionView.collectionViewLayout.invalidateLayout(with: context)    UIView.animate(withDuration: 0.3) {        self.collectionView.layoutIfNeeded()    }